Note: Descriptions are shown in the official language in which they were submitted.
WU 96128265 cA 02214686 2005-oi-07 pCTlUS95IOZ988
SELF-ADJUSTIrTG HEAD
The present invention relates to fastener installation systems, and more
particularly
relates to systems for sensing the improper installation of a fastener.
BACKGROUND OF THE INVENTION
Installation systems for installing hardware (such as fasteners) to metal
panels, are
well known in the art. For example, U.S. Patent No. 4,765,05? discloses a self
attaching
fastener, panel assembly, and installation apparatus. Also, U.S. Patent No.
4,505,416
discloses a fastener installation apparatus for installing fasteners,
particularly pierce or clinch
nuts, in a reliable, simplified fashion.
Although the above-referenced patents disclose systems for installing
fasteners, they
all rely on the assumption that once the fastener installation apparatus is
properly "set up"
for a given style of fastener, a given panel metal thickness, and other
related parameters, all
future applications having such parameters will result in acceptable
installations. Although
this assumption is accurate in many applications, there are instances where it
is highly
desirable to automatically adjust certain features of the installation
apparatus to ensure the
highest quality installation.
One problem frequently encountered in fastener installations is variations in
the panel
thickness. Normally. the installation apparatus, which has an installation
head mounted to
one of the platens of a press, is pre-adjusted for a certain specified
thickness of metal, such
as steel. However, the thickness of the material is not constant and, in fact,
can vary widely,
even though within acceptable tolerances. For example, hot rolled steel sheets
having a
width of 300mm to S lOmm have a thickness tolerance of plus .25mm for a
thickness of
1.43mm to 1.14mm. As should be appreciated, this amount of variation can
affect the
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performance of the installed fastener. In this example, the surface of the
steel sheet which
is engaged by the fastener head can vary from between 0 to .25mm. In this
range, the
installation head will hit the material with varying force from light to heavy
depending upon
the panel thickness, which is varying between 0 and .25mm. A force between
light and
heavy is the ideal installation force with the light and heavy hits being
undesirable.
Another problem encountered in fastener installations is machine or press
drift from
a set shut height. This drift of the press from a preset shut height can be
due to many
factors, but is commonly due to press wear. There is little or no control over
press drift,
with the consequences being improperly installed fasteners.
A still further problem can occur in larger presses wherein it is difficult to
control the
parallelism of the platen with respect to the bolster. With more than one
installation head,
if the platen stroke is not parallel with respect .to the bolster, light and
hard hits will result
and produce improperly installed fasteners.
Although it is possible to vary the shut height of the press, this is not a
feasible
solution in applications that are having more than one operation performed in
a single stroke,
which is the typical situation. The shut height is measured when the press is
bottomed out,
or shut, and is the distance between the bottom face of the platen and the top
face of the base
on which the panel to be worked is resting. This shut height is predetermined
and can only
be varied by changing the location of the rams; i.e., moving them with respect
to one
another. If the shut height is varied, it will affect all other operations,
possibly compounding
the adverse effect on the operations being performed on the panel.
What is needed is an apparatus and method that individually adjusts, and in
some
applications, automatically adjusts the affected nut installation apparatus to
account for
variations in the thickness of the material. In this way, thickness variations
across the width
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and the length of the material can be monitored and adjustments made to ensure
uniform
installation of fasteners in a panel.
In addition to the variance in nominal panel thickness, there are other
factors which
could affect the integrity of the joint made between a fastener and a panel.
Some of these
factors include a broken or misaligned installation apparatus or fastener, the
use of improper
material (both fastener and panel), normal wearing of the installation tools,
etc.
Thus, in view of the above, it is an object of this invention to provide a
system for
installing fasteners into a panel wherein the system senses one or more
operational
parameters and can individually adjust installation apparatus in response to
the sensed
parameters to ensure a consistent, high integrity joint between the fastener
and panel.
Another object is to record, restore, and maintain statistical process control
data on every
panel as opposed to random sampling.
~UMIViARY OF THE INVENTION
In light of the foregoing objects, the present invention provides a system for
installing
fasteners into a panel which includes an adjustable installation apparatus. It
should be
understood that the adjustment can be made either automatically or manually.
Force sensors
are included in the installation apparatus for sensing the forces exerted by
the installation
apparatus when it installs fasteners into a panel. The force exerted by the
installation
apparatus is compared to the force which is normally expected to be exerted in
such an
installation. If the difference between the expected force and the actual
installation force
~ varies by a predetermined amount, the installation apparatus in the
preferred embodiment can
. be adjusted or is automatically adjusted so that in subsequent
installations, the force exerted
by the installation apparatus will generally correspond to the predetermined
force. With
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manual adjustment, the preferred system would include an indicator or read-out
for indicating
when the adjustment is complete for optimal performance.
In addition to being able to adjust the installation apparatus, the present
invention also
includes control means which can disable the press in response to the relative
position of the
fastener with respect to the installation apparatus. The control means is
responsive to the ~
position of the fastener with respect to the installation apparatus and if the
fastener is not
properly positioned or is not available it will shut down the press. The
system of the
preferred embodiment will indicate, through an indicator panel, the reason for
shut-down so
that corrective action can be taken.
The fastener installation apparatus of this invention includes a control means
with
adjacent moveable members. These members are moveable in directions generally
perpendicular to one another in response to the movement of the other. One of
these
movable members engages either the plunger or the die button and moves it with
respect to
the other to adjust the distance between the plunger and the die button.
In the preferred embodiment, the control means includes a threaded member
coupled
to one of the members and a motor operatively engaging the threaded member to
rotate the
threaded member to move one of the members relative to the other member.
The fastener installation apparatus includes a sensing means for sensing the
force
being applied against the fastener and the panel. A comparator is provided
that compares
the sensed force with a predetermined force which corresponds to the optimal
force for
fastener attachment. The comparator produces a result and the control means
reacts to this
produced result and adjusts the operative length of the installation apparatus
or disables the
press in response to the result. The sensing means includes a strain gage load
cell for
collecting the force information.
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In a further embodiment, the control means includes an eccentric cam coupled
to the
adjustable member and a motor operatively engaging the eccentric cam to rotate
the cam.
By rotating the cam, the adjustable member is moved to compensate for the
varying
thicknesses of the panel. As in the preferred embodiment, if the fastener is
positioned
. 5 incorrectly of isn't available, the press will be disabled so that
corrective actions may be
taken.
In a still further embodianent, the control means includes a wedge disposed
against
the adjustable member and a motor operatively engages the wedge to move the
wedge and
change the position of the adjustable member.
In the preferred system, the adjustable member is the plunger in the
installation head.
However, as indicated above the die button could be the adjustable member.
Other advantages and meritorious features of the present invention will become
more
fully understood from the following description of the preferred embodiments,
the appended
claims, and the drawings, a brief description of which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures lA-1D depict four essential phases encountered when installing a
pierce
fastener in a panel.
Figure 2 is a graphical representation of a nominal force signature.
Figure 3 is a graphical representation of a nominal force signature bounded on
its
upper side by a thick metal force signature and bounded on its lower side by a
thin metal
force signature.
Figure 4 is a graphical representation of a nominal force signature bounded on
its
upper side by a misalignment force signature.
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Figure 5 is a schematic representation of the self adjusting head of the
present
invention.
Figure 6 is a block diagram of the electronic control portion of the self
adjusting head
of the present invention.
Figure 7 is a flow chart depicting the learn phase of the present invention.
Figure 8 is a graphical representation of a nominal force signature bounded by
high
and low error bands.
Figure 9 is a flow chart depicting the learn phase of the present invention.
Figure 10 is a second embodiment of the servo-mechanism of the present
invention.
Figures 11 A-C is a third embodiment of the servo-mechanism of the present
invention.
Figure 12 is an embodiment illustrating an adjustable die button.
Figure 13 is a cut-away view of the die button and sensing device.
Figure 14 is an exploded perspective view of the adjustable head of the
present
invention.
Figure 15 is an exploded perspective view of the die button and sensing
device.
Figure 16 is a view of a further embodiment of the adjustable head of the
present
invention.
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3
I D F P
T
Now referring to Figure lA, a typical installation apparatus for installing
fasteners 20
into panel 22. The panel includes a plunger 24 and die 26. Plunger 24 is part
of the
installation head which is attached to a press which is capable of generating
several thousand
pounds of force against plunger 24. A typical installation cycle is depicted
in Figures lA-1D
and includes locating fastener 20 and panel 22 between plunger 24 and die 26
(see
Figure lA), driving plunger 24 toward die button 26, wherein fastener 20 and
panel 22 are
forced together (see Figure lA), further driving fastener 20 into panel 22
such that pilot
portion 32 of fastener 20 pierces through panel 22 thereby dislodging slug 30
through die
opening 28 (see Figure 1B), driving fastener 20 into panel 22 such that panel
22 is driven
into recessed portions 34 of fastener 20, thereby forming positive engagement
between
fastener 20 and panel 22 (see Figure 1 C) and then applying additional force
to fastener 20
and panel 22 to set fastener 20 and panel 22 (see Figure 1D). A complete
disclosure of such
an installation system is disclosed in U.S. Patent Nos. 4,630,363; 3,648,747;
and
4,484,385,
Now referring to Figures lA-1D and Figure 2, if a load sensing device 36 (such
as
a strain gage load cell) is placed below die 26 and multiple installations
took place, a series
of force signatures 38 would be generated as disclosed in Figure 2. Figure 2
discloses a
family of eight separate force signatures superimposed on the same graph.
Although each
of the eight installations involve fasteners of the same design and panels
having the same
nominal thickness, small variations in panel thicknesses, fasteners, etc.,
cause each of the
eight curves to be slightly different from the other curves in the family. The
upper and
lower bounds of force signature 38 define the bounds of all nominal
installations for a given
fastenerlpanel combination. The group of signals are appropriately termed the
nominal force
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signature because each signal, although having its own variance with other
signals, share
common characteristics--which, if present, provide indications that the mating
of fastener 20
to panel 22 is properly accomplished. Each phase of installing fastener 20 to
panel 22 will
now be discussed in conjunction with the force signatures generated therein.
Now referring to Figures 1-4, when plunger 24 first forces fastener 20 against
panel 22, the force monitored by sensing device 36 rises sharply 40
(substantially vertical in
Figure 2). As plunger 24 moves through the first phase (or zone 1) of the
installation
process, the load experienced by sensing device 36 increases substantially as
shown in zone 1
of Figure 2. The beginning of zone 2 is earmarked 42 by a sharp increase in
load. This
sharp increase in load is due to the piercing of panel 22 by pilot portion 32
of fastener 20.
Zone 3 depicts the characteristic force necessary to form panel metal 20 into
recessed
portions 34 of fastener 20. Lastly, zone 4 indicates the "setting load," which
is the load
necessary to place fastener 20 in final engagement with panel 22.
Now refernng to Figure 3, once nominal force signature 38 is established, it
is easy
to determine if a particular installation is satisfactory. For example, if the
nominal force
signature 38 is compared with two actual force signatures 44 generated using
metal which
is thicker than that found in the nominal range, an obvious difference in
force signatures is
apparent. Likewise, when nominal force signature 38 is compared with two
actual force
signatures 46 generated using thin metal, an easily detectible downward and
leftward shift
takes place in the force signature. Figure 4 discloses misalignment signature
48, wherein
fastener 20 was deliberately misaligned with die button 26. The difference in
signatures 48
and 38 is particularly acute when viewed across zone 3.
In view of the above disclosure, it is understood that a force signature can
be
generated which is characteristic of the nominal forces present during the
installation of a
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fastener to a panel. It has also been illustrated that certain, undesirable
conditions may
present themselves and may be detectible by monitoring the actual force
signature generated
during a given installation and comparing that actual force signature to the
nominal signature.
If the actual force signature deviates from the nominal force signature beyond
predetermined
limits, corrective action may be taken. The following portion of this
dixlosure sets forth
a system which monitors the difference between a nominal force signature and
an actual force
signature and automatically takes corrective action if the actual force
signature deviates from
the nominal force signature beyond predetermined limits.
With reference to Figure 5, self adjusting head 50 includes electronics
portion 52,
servo-mechanism 54, and force sensor 36. Force sensor 36 generates an
electronic output
signal along line 56, representative of the force exerted by plunger 24 during
the installation
process. Signal conditioning and control electronics 58 is responsible for
converting the
force signal present on line 56 into a useable format (preferably digital
format) and also
conducting the comparison between nominal force signature 38 and actual force
signatures
generated by sensor 36. Control electronics 58 can be programmed to indicate
certain error
conditions by way of illuminating one or more lights 62, 64, 66, 68, 70 and 72
on error
conditioned diagnostic panel 60. Signal conditioning and control electronics
58 can also
be programmed to disable the press, press disable controls 74 upon the
occurrence of
predetermined error conditions. Signal conditioning and control electronics 58
is also
capable of outputting an electronic signal along line 76 so that an external
recorder or
monitoring device 78 can be used to create a permanent record of a force
signature,
commonly referred to as the statistical process control data or SPC, for each
stroke of the
press.
One primary function of signal conditioning and control electronics 58 is to
monitor
the output of force sensing device 36 and to generate, along line 80 the
appropriate correction
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signal to servo-mechanism 54, or if manual adjustment is used to send the
information to an
indicator that can indicate the amount of adjustment needed or indicate when
enough
adjustment has been done to correct the problem.
One such example of this corrective technique will now be explained in
conjunction
with Figure 3. Assume that self adjusting head 50 has been programmed to
expect to receive
an actual force signal as defined by the bounds of nominal force signature 38
in Figure 3.
Additionally, assume that, in fact, signal conditioning and control
electronics 58 receives a
force signature falling within the bounds of thin metal signature 46. Signal
conditioning and
control electronics 58 is programmed to recognize that the signature being
received is
characteristic of a thin panel condition and take corrective action. A
corrective error signal
is generated by signal conditioning and control electronics and sent along
line 80 to
servo-mechanism 54: As illustrated in Figure 5, adjustable-mechanism 54 is
comprised of
motor 82, gear drive 84, and lag screw 86. The corrective signal sent along
line 80 causes
motor 82 to turn in the appropriate direction, thereby causing plunger 24 to
extend
downwardly by the appropriate magnitude. Thus, by extending plunger 24
downwardly, the
thin metal condition is compensated for and once again fasteners 20 can be
installed in
panel 22 to yield an installation of acceptable integrity. Of course, under
some error
conditions, the upward or downward adjustment of plunger 24 will not correct
the problem
at hand. For example, in Figure 4, signature 48 represents a signature caused
by
misalignment of die button 2b and fastener 20. No amount of vertical
adjustment of
plunger 24 will correct for a misaligned condition. Under such a condition,
signal
conditioning and control electronics 58 would simply generate the appropriate
signal to error
condition diagnostic panel and along line 88 to initiate the disablement of
the press, press
disable controls 74.
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Now referring to Figure 6, signal conditioning and control electronics 58
preferably
includes microprocessor controller 90. Microprocessor controller 90 is
programmed to learn
the nominal force signature 38, to monitor the actual force sensed by sensor
36, and to
output the appropriate signals to error condition diagnostic panel 60, press
disable controls
~ 5 74 and adjustable-mechanism 54. Signal conditioning and control
electronics 58 has two
primary modes of operation--learn mode and operate mode. Both modes will now
be
discussed.
Learn Mode
Now refernng to Figures 4-8, to initiate the learn mode, the learnloperate
command
switch 92 is activated by the system operator. This indicates to
microprocessor controller 90
that the operator wishes to teach microprocessor controller.the nominal force
signature 38
for the particular installation process at hand. Figure 7 sets forth the three
primary steps
involved in executing the learn mode. First, as a number of fasteners are
installed into
panels and, for each installation microprocessor controller 90, reads and
stores the actual
force signature. Microprocessor controller 90 can store this information in
graphical format
or tabular format. The information is analyzed to determine the envelope of
the nominal
force signatures. The envelope of nominal force signature curve is exemplified
as 38 in
Figure 4. Nominal signature 38 is divided into zones 96 (see Figure 8) and an
acceptable
high and low error band 100, 102 is defined and associated with each zone.
The generation of a high/low error band can be either automatically generated
by the
software, based on past knowledge of the installation process, or may be
manually input
based on data collected from simulated error conditions. For example, in
reference Figure 3,
force signature 46 was generated by placing a fastener into an undersized
panel. Likewise,
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force signature 44 was generated by inserting a fastener into an oversized
panel. Thus,
knowing the characteristics of the thin and thick metal signatures, error
bands can be
constructed around nominal signature 38 such that a force value occurnng
between the error
bands indicates an acceptable installation, and a force value occurring
outside the error bands
indicates an unacceptable fastener installation. It is also apparent that
selected zones may be
more appropriate for making pass/fail determinations than other zones. For
example, in
Figure 3, zone 1, the thick metal signature 44 does not make any substantial
separation from
nominal signature 38. It is not until zone 2 that a separation occurs. Thus,
it appears that
zone 1 would not be the preferred zone to make a determination for a thick
metal signature.
Likewise, misaligned signature 48 achieves its maximum separation from nominal
signature 38 in zone 3; thus, zone 3 appears to be the most beneficial zone
for determining
the occurrence of a misaligned error condition. It is evident from the error
conditions
illustrated in Figures 3 and 4 that the force signature associated with each
error condition has
its own characteristics. By programming microprocessor controller to monitor
key
characteristics, not only can microprocessor controller 90 determine when an
error condition
occurs, but it is also capable of determining what kind of error condition
occurred. This
information can be displayed to the user via terminal 104 and/or error
condition diagnostic
panel 60. This type of information is invaluable when diagnosing the cause of
improper
fastener/panel installations.
~nerate Mode
Now referring to Figures 7-9. After the learn mode (see Figure 7) has been
executed
and the nominal force signature 38 is generated (along with the error band
associated with
each zone), self adjusting head 50 is ready for operation. Thus,
microprocessor controller 90
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holds in a wait loop 104, 106 waiting for the first fastener to be installed.
Upon the
commencement of an installation cycle 106, microprocessor controller 90
collects and stores
the force signature associated with the actual installation cycle 108. The
stored signature is
divided into zones which correlate in time with zones 96 defined during the
learn mode.
Preferably, these zones are defined as fixed time segments within one
installation cycle. An
installation cycle is defined as that time commencing with plunger 24
contacting fastener 20
and ending at such time as plunger 24 no longer contacts fastener 20. Next,
the actual load
signature associated with each zone is compared to the error band associated
with that zone
to determine whether it falls within the error band or outside of the error
band. If the
signature falls within the error band 114, there are no error conditions
present, and controller
90 returns to the wait state 104, 106. If there are error conditions present,
the particular
error condition is diagnosed 116 (e.g., thick panel, thin panel, misalignment,
etc.) and the
appropriate error condition code or codes are transferred to error condition
diagnostic
panel 60 and/or terminal 104. Based on the type of error condition presented,
a
determination is then made whether or not to disable the press 118. If it is
the type of error
condition (e.g., misalignment condition) that calls for press disablement, the
appropriate
signal is sent from microprocessor controller 90 over line 88 to press disable
control 74,
wherein the press is disabled 120. If the existing error condition is one in
which the press
does not need to be disabled, microprocessor controller 90 executes the stroke
adjustment
logic 122 and outputs the appropriate command 124 to servo-motor amplifier.
In a prototype of the present invention, it was found that zones 1 and 2 were
useful
for detecting error conditions which could not be corrected by adjusting
plunger 24. Thus,
zones l and 2 were primarily used to test for conditions which would justify
shutting down
the press. Zones 3 and 4 were most useful in detecting conditions which could
be rectified
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by adjusting plunger 24. Preferably, the installation signature is divided
into four zones
wherein:
1. Zone 1 is used for monitoring panel presence; if the panel is missing the
press
shuts down.
2. Zone 2 is used for monitoring piercing load; if the die is defective or
materials
is too hard, too soft, etc., the press shuts down.
3. Zone 3 is used for monitoring the forming of metal into nut; if an error
condition exists, the plunger is adjusted up or down according to the error
control strategy.
4. Zone 4 monitors setting load; if an error condition exists, the plunger is
adjusted up or down according to the error control strategy.
Although many schemes can be employed in stroke adjustment logic 122, the
simplest
scheme is to compute the difference between the average nominal force
signature for a given
zone and the average actual force signature for a given zone. This difference
could then be
multiplied by a gain factor and the result of the multiplication could then be
added to an
offset factor figure. This type of error correction scheme is known as
"proportional control"
and is well known to those skilled in the art. The value of the gain figure
and the offset
figure could be empirically determined by measuring the actual amount of
plunger 24 travel
that must be effectuated to correct for an error condition of a given
magnitude. Of course,
other, more sophisticated control schemes may be used involving integral and
derivative
terms, etc. Such sophisticated control schemes are well known to those skilled
in the art of
adjustable-motor controls.
The following error conditions are detectible using the self adjusting head of
the
present invention:
A. Metal thickness tolerance drift.
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B. Broken die button.
C. Misalignment between the fastener and
the die button.
D. Improper die button.
E. Improper material hardness.
F. Missing nut and/or panel.
G. Excessive tool wear.
H. Drift in press adjustment or setting.
I. Improper or malformed nut or fastener.
Alternative Embodiments of Servo-Mechanism
As more fully described above, a first embodiment of adjustable-mechanism 54
is
disclosed in Figure 5 and includes adjustable motor 82, gear drive 84, and
screw thread 86.
With reference to Figures 10, 14, and 15, the preferred embodiment of an adj
ustable
mechanism S4 is illustrated. Mechanism 54 includes a first wedge 120, which
engages a
second wedge 122. The first wedge 120 is attached to a screw thread 126, which
is, in turn,
coupled to motor 82 (see Figure 14). As motor 82 receives an error correction
signal along
line 80, motor 82 rotates its output shaft thereby causing screw 126 to
rotate. Rotation of
screw 126 causes wedge 120 to move laterally. Because surface 132 is inclined
with respect
to the centerline of wedge 120, the lateral movement 128 of wedge 120 causes
vertical
movement of plunger 24. Thus, the preferred embodiment of adjustable-mechanism
54 is
effective for providing vertical movement of plunger 24.
Continuing with Figures 14 and 15, an exploded perspective view of the
adjustable
. head 50, die button 26, and the load sensing device 36 will be described.
The adjusting
head SO includes a nose sub-assembly 200, a shank sub-assembly 202, and a base
sub
i __
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assembly 204. The nose ~tib-assembly 200 includes a nose body 2u6, nut holder
fingers 208,
and a nose plate 210. Nut holder fingers 208 are pivotally mounted within nose
body 206
to receive and hold a nut to be installed.
The shank sub-assembly 202 includes a punch housing nose shank 214. Nose
shank 214 is attached to nose sub-assembly 200 by screws 212 (only one screw
is shown).
The base sub-assembly 204 includes a punch support base 216, a back-up plate
218,
and a nut plunger 24. Back-up plate 218 is bolted to base 216. Screws 222
attach plate 220
to base 216. A punch housing shank stop pin 224 is mounted in the rear of the
punch
support base 216. Pin 224 is retained by a plate 226 and screws 228. Only one
is
illustrated.
In operation, the base sub-assembly 204 is mounted to one of the platens of
the press.
As the press closes, the nut plunger 24 pierces a nut through a panel
positioned on the die
button 26. The nose shank 214 reciprocates within base 216 as the press opens
and closes.
This reciprocation forces the nut plunger 24 into the nose body 206, and
against a nut to
pierce the nut through the panel. The movement of shank 214 relative to base
216 is adapted
to control a mechanical Reel-Feed assembly, not illustrated. (Reel-Feed is a
registered
trademark of Multifastener Corporation.)
Referring to Figures 13 and 15, the die button 26 and load sensing device 36
will be
described further. The die button 26 is mounted within retainer 230. A
retention key 232
and screw 233 retain die button 26 in retainer 230. Mounted below die button
26 is a load
sensing device 36. In the preferred embodiment, load sensing device 36 is
mounted within
a back-up plate 234. In this embodiment, the sensing device 36 is pressed into
an opening
in back-up plate 234. It should be appreciated that the sensing device 36
could be molded
directly into plate 234 or mounted in various other ways, of knowledge to
those of ordinary
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WQ 96!28265 PCT/US95/02988
skill in the art. An electrical lead 236 is received within an opening 237 in
plate 234 to the
electronics portion 52. Guide pins 238 and screws 240 are used to mount the
retainer 230
to a platen 242. In the preferred embodiment, plate 234 is mounted to retainer
230 by, for
example, screws.
~ Figures 11A-11C disclose a further embodiment of adjustable-mechanism 54.
This
embodiment employs an eccentric cam 136, having head 138, which is rotatable
by way of
a hand tool. In the disclosed embodiment, the cam head 138 is intended to be
manually
adjusted. Once adjusted, a locking tab 128 can be locked by tightening bolt
134. Plunger 24
is biased against eccentric cam 136 by way of bias springs 140. When cam head
138 is
rotated, eccentric cam 136 rotates about axis 142. Because outside surface 144
of
eccentric 136 is not concentric with axis 142, outside surface 144 causes
plunger 24 to move
laterally 134. This lateral movement is effective for adjusting the plunger as
has already
been discussed.
With reference to Figure 12, a still further embodiment of the present
invention is
illustrated. In this embodiment, the adjusting device 175 is positioned under
the die
button 26. The adjusting device 175 includes a wedge 177 sandwiched between
wedge 179
and a plate 173, which is illustrated as a second wedge. It should be
understood that
plate 173 could be a flat plate, if desired. A screw thread 181 is attached to
wedge 177.
rotation of screw thread 181 causes wedges 179 to move die button 26
longitudinally. As
should be appreciated, the screw thread 181 can be turned manually or by a
screw-motor.
In this way, die button 26 can be adjusted to compensate for variations in
material thickness.
With reference to Figure 16, a modification to the self adjusting head 50 of
the
present invention is illustrated. The modification includes a potentiometer
302, which is
operatively connected to the adjusting motor 304 and to a data display or
recording device
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WO 96128265 PCT/US95/02988
to electronically record the adjustment of the plunger 24. The motor 304 and
potentiometer 302 are preferably mounted to head SO in a known conventional
manner. The
data display or recording device is illustrated as a separate box from the
control, but it could
be included in the control. In the preferred embodiment, the potentiometer 302
is
manufactured by Allied Electronics, Inc. , and is sold by catalog designation
item no. 1220-
502. The preferred potentiometer 302 has a 20-turn pot. An alternative
potentiometer is
available from the same manufacturer and is identified by catalog item no.
1000-502 and has
a 10-turn pot. Potentiometer 302 is preferably interconnected to adjustment
motor 304
through spur gears 306. In the preferred embodiment, when a 20-turn
potentiometer is used,
the spur gears have a ratio of 1:1. When a 10-turn potentiometer is used, the
spur gears
have a ratio of 2:1. In the preferred embodiment, the spur gears are Browning
spur gears,
identified by number NSS2430A (1.250 p.d.n.). The motor used in the modified
embodiment is purchased from Micromo Electronics, Inc., and is identified as a
Micromo
Gear Head Series 34PG with Motor No. 2233, Micromo Part No. 2233V048ST34PG
90:1 +X0429.
The use of the potentiometer 302 allows the vertical overall adjustment of
plunger 24
to be electronically monitored and, if desired, recorded. The information from
the
potentiometer can be used to determine the range that plunger 24 has been
adjusted during
a predetermined time period. Information as to the range of movement of the
plunger can
enable an operator to fine tune the adjustable head to reduce the amount of
vertical movement
of the plunger 24 and further optimize the installation process. For example,
if the operator
discovers that the adjustable head is adjusting the plunger over a certain
distance, the
operator could preadjust or program the installation head to adjust the
plunger to the middle
of the range and reduce the amount of overall vertical movement of the plunger
during
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CA 02214686 1997-09-04
W~ 96128265 PCT/iJS95/02988
operation. Additionally, the potentiometer readouts could be saved and
information obtained
from numerous readouts with regard to specific steel types. With this
information,
depending upon the steel being processed, the adjustable head could be
preadjusted to take
into account known initial variations in thicknesses to reduce the amount of
overall
- 5 adjustment of the vertical member. This adjustment could be done manually,
based upon a
visible readout from the potentiometer, such as a digital readout, or
automatically, by
powering the motor 304 based upon the voltage output from potentiometer 302.
The control
would receive the potentiometer information, preferably in the form of a
voltage, and, based
upon the information, automatically adjust the motor.
The use of the potentiometer is also advantageous in informing the operator of
overall
adjustments being made. During normal operation of the adjustable head, the
operator would
have the ability to receive information from the potentiometer from, for
example, a digital
readout, either continually or intermittently. In this way, the operator has
the ability to
determine the position at which the plunger is operating within the overall
range of
adjustability at that point in time to ensure that there is still room for the
system to adjust
both positively and negatively to optimize fastener installation during
operation.
The foregoing detailed description shows that the various embodiments of the
present
invention are well suited to fulfill the objects of the invention. It is
recognized that those
skilled in the art may make various modifications or additions to the
preferred embodiments
chosen here to illustrate the present invention without departing form the
spirit of the present
invention. For example, although sensing device 36 is shown residing below die
button 26,
. it may operate satisfactorily above plunger 24. Accordingly, it is to be
understood that the
subject matter sought to be effective protection hereby should be deemed to
extend to the
subject matter defined in the appended claims, including all fair equivalents
thereof.
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